Most motor vehicles are fitted with an internal combustion engine which usually provides for the drive of the vehicle. Such an internal combustion engine, preferably when this is fitted as a piston engine, has a crankcase. Located in the crankcase is a crankshaft which is connected to pistons of the individual cylinders of the internal combustion engine via connecting rods. Leaks between the pistons and the appurtenant cylinder walls result in a blow-by gas stream by means of which blow-by gas passes from the combustion chambers into the crankcase. In order to avoid inadmissible excess pressure in the crankcase, modern internal combustion engines are fitted with a crankcase ventilation apparatus in order to remove the blow-by gases from the crankcase.
In order to reduce harmful emissions, with the aid of the crankcase ventilation apparatus the blow-by gas is not supplied to the surroundings but usually to a fresh air system of the internal combustion engine which supplies the combustion chambers of the internal combustion engine with fresh air.
An oil mist prevails in the crankcase so that the blow-by gas entrains oil. This oil in the form of oil droplets can damage elements in the intact tract such as for example a turbocharger. In order to protect these elements and reduce the oil consumption, the crankcase ventilation apparatus usually has an oil separating device and preferably an oil return which returns the separated oil to the crankcase.
In the case of crankcase ventilation apparatuses, a distinction can fundamentally be made between passive systems and active systems. Passive systems use the pressure difference between the crankcase and the negative pressure of the fresh air system to drive the blow-by gases. Active systems additionally produce a negative pressure for extracting the blow-by gas from the crankcase. As a result, a higher pressure difference can be used for the oil separation so that the separation is improved. The pressure differences which can be achieved in this way are nevertheless limited since the maximum negative pressure which can be produced is limited.
It is the object of the invention to provide an improved or at least different embodiment for a pump device of the type mentioned initially which in particular is characterized by an increased efficiency with regard to oil separation.
This object is solved according to the invention by the subject matters of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.